River that joins the Seine on the edge of Paris, offering a barrier to armies invading France from the north. Scene of a pivotal early battle in the First World War in September 1914, which resulted in German forces withdrawing from the Marne to the River Aisne, thus destroying any chance of implementing the Schlieffen Plan. In the Ludendorff offensive of March-July 1918, the French army was driven back to the Marne, but once again the river proved to be the closest that the German army would get to Paris.

Marne is a department in north-eastern France named after the Marne River which flows through the department. The prefecture (capital) of Marne is Châlons-en-Champagne (formerly known as Châlons-sur-Marne). The subprefectures are Épernay, Reims, Sainte-Menehould, and Vitry-le-François.